Any suggestions for an air conditioner that freezes up? It ran fine until the 90 degree heat hit - then it froze up. I defrosted it with a blow dryer and it ran fine again, but the next day it froze up again. Is there anyone out there with HVAC experience that could give me an idea of what would cause the unit to freeze up? It literally had ice covering the coils and that is what caused it to shut down. Thanks.

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Any suggestions for an air conditioner that freezes up? It ran fine until the 90 degree heat hit - then it froze up. I defrosted it with a blow dryer and it ran fine again, but the next day it froze up again. Is there anyone out there with HVAC experience that could give me an idea of what would cause the unit to freeze up? It literally had ice covering the coils and that is what caused it to shut down. Thanks.

Low refrigerant is the likely cause. Oddly enough, my heat pumps will freeze up in the 30's, but the A/C side works fine.

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Most likely the problem is not low refrigerant. The units are sealed (hermetic) and seldom loose refrigerant unless you have a pin hole leak from vibration or corrosion.

The usual problem with freezing up is low air flow across the evaporator. Do you clean the filter regularly and check to see if the coil is clean? Don't run the fan on low speed as it is more likely to freeze due to low air flow.

A simple check to see if the unit is cooling Ok is to start the unit and run it on high fro about 10 minutes. Check the temperature of the air entering the unit and then the air leaving a duct near the unit. The leaving air should be 15 to 20 dF lower than the entering air. If it is more, you may have reduced air flow or possible low on refrigerant.

We often find that the unit are short cycling the discharge air back into the return air allowing the evaporator temperature to subcool and freeze up. CHeck to be sure the return area of the ceiling pacakge is well seperated (use metal foil tape) to seal off this area from the dischage side of the ceiling package. Make sure coil is clean, if ducted not vents are closed, run fan on high and try to keep humidity down. GOod luck and keep us posted as to the outcome. as best possible

Mike,
I have a question for you. When I look up into the AC unit, there are two sides to the unit. Is one of them the discharge side and the other side the return side? If that is the case, I also see a piece of foam covered with metal foil. It is about 5" by 8" and is about 1" thick. What is the purpose of this foam piece? Also, I am not sure where that foam piece should be positioned in the unit. Thanks for your help!

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Darrell & Mel:
Any suggestions for an air conditioner that freezes up? It ran fine until the 90 degree heat hit - then it froze up. </div></BLOCKQUOTE>
Our experience, when our AC froze up (non-ducted, roof mount), was to back off the temperature control a little. Rather than putting it in the most extreme "cold" position, we run it with about 1/8" from that post. This gives the compressor time to cycle off & on, giving it time to "de-ice" if necessary. It has never iced up in the past 4 years since we started this procedure.

We are in humid Branson, MO right now, and inside the trailer it is 72 degrees, 60% humidity. Outside it is 80 degrees, 85% humidity. It was warmer during the day and is cooling off now because of some showers, but the AC continues to keep the trailer consistently cool.

9 out of 10 RV A/C freeze ups are low air flow, and seldom low refrigerant. Look first at low air flow due to restricted filters, low fan speed, dirty evaporator coil or bypassing air between the inlet and out let of the unit.

The units are factory sealed (hermetic) and are not easily checked or repaired by the normal shade tree mechanic. People will use the short cut of a saddle clamp and add some refrigerant. Problem is the saddle clamps are bad leakers. you have to use one to access the system and clear the refrigerant. then you have to solder in two Schrader valves with low pressure N2 flowing in the lines to prevent oxidization inside due to the heat. Next you use a vacuum pump and pull the system into a deep vacuum to get the moisture and air. Then you finally recharge the system with refrigerant.

The easiest thing to do is check for low air flow. When operating correctly, there should be about a 20 dF difference between inlet air and outlet air on the unit.

Thanks for the information. What I found today as I was working on various things on my coash is that the flow divider (or baffle) that is supposed to separate the inlet from the outlet was not positioned properly, and was allowing air flow to go directly from the outlet (ducted side) to the inlet (or return side). So I repositioned the flow divider and ran the unit for two hours today with no freezing up. Now I am looking forward to running the unit during a hot summer day for several hours, but I think the flow divider was the culprit.

This is what I love about this site. All the good knowledge here. My AC froze up twice last summer while I was in Florida. I "assumed" it was low on refrigerant myself, and knowing it is a sealed unit, wondered who or how to fill it. Before going to that extreme though, I removed top and bottom covers, blew everything out good, cleaned the filter, tightened up the floppy air deflectors, and carefully put everything back together. I have not had a problem since. Had to be an airflow problem that was fixed with the cleaning.